As one of the hallmarks of New Nordic cuisine, foraged ingredients are now trending in restaurants across America. But Swedish native Fredrik Berselius, chef at Aska in Williamsburg, Brooklyn, has been eating wild produce since he was a kid growing up in Stockholm. Today, as part of Brooklyn’s Food Book Fair (which runs through the weekend), Berselius will take part in the show-and-tell Food + Foraging panel.

“Foraging is not uncommon in Sweden,” says Berselius. “I remember picking out mushrooms, and either pickling them, or just having a mushroom sandwich with a mountain of them. Same with lingonberries and blueberries, except we made jams and jellies out of them.” Now based in New York, Berselius travels upstate to find ingredients like chickweed (which tastes “almost like a sprout”), wild spinach and nutty morel mushrooms. "Many people don’t know this, but half an hour from Manhattan, you can find a lot of greenery, especially in national parks."

Here, the Aska chef shares some tips for novices considering a culinary treasure hunt in the Northeast. One key rule to follow: Don’t eat anything without first consulting an expert or doing heavy research to make sure it's safe to eat. As reference books, Berselius suggests Miles Irving’s The Forager Handbook and Euell Gibbons’s Stalking the Wild Asparagus. “There have been a couple of scares, where I’ve been like, ‘Uh-oh, was that not so good to eat?’ But usually I’m more concerned with running into mountain lions.”

EASIEST PLANTS TO FORAGE

Chickweed. “It tastes grassy, a little corn-like—almost like a sprout. We use it here with pike roe. It’s also good with egg yolk.”

Nettles. “They’re perfect now in the spring. They’ve got a round, spinach-y flavor. You can serve them with fish. In the restaurant, we serve them with milk and burnt hay.”